According to a new study, conservative Muslim dress codes might be causing serious health problems for Muslim women:

In certain Middle Eastern and other countries where conservative dress curtails exposure to sunlight, high levels of vitamin D supplementation may be needed to raise serum levels sufficiently in women, investigators report.

“When sunlight exposure — the main source for vitamin D in humans — is limited,” Dr. Hussein F. Saadi said, “much higher dietary intake of vitamin D is needed than currently recommended,” especially for women who are breast-feeding.

As reported in the June issue of the American Journal of Clinical Nutrition, Saadi and colleagues at the United Arab Emirates University, Al Ain, studied vitamin D levels in 90 women who were breastfeeding and 88 women who had never given birth. Many dressed to cover their whole bodies, including their hands and faces, while outside of their homes.

Only two of the women, one in each group, were not vitamin D deficient at [the time of the] study.

Studies like this are why I’m skeptical of any theory which attempts to yoke our cultural practices to the adaptive pressures of natural selection. Until proven otherwise, I tend to assume that our specific cultural habits and traditions are simply the product of idiosyncratic and incomprehensible historical forces operating on our culture directly, and have little or nothing to do with reproductive fitness way back when. After all, it’s hard to construct a biologically rigorous theory of culture or religion that can explain why someone might willingly cloak themselves in a black covering (in an area dominated by hot deserts) and put themselves at high risk for a variety of serious illnesses caused by vitamin D deficiency.

When trying to comprehend the practices of any given religion, I think we are better off talking about various 14th century imams and Vatican councils and ancient Greek philosophers than we are talking about spandrels and agent-detection modules. As Daniel Dennett says, religion is a thoroughly natural phenomena, but that doesn’t mean that evolutionary biology is the best way to understand it. Sometimes, what we need is good old fashioned cultural history.